Market voices on:

Levels of large particulate matter, known as PM 10, hovered around 900 in the late morning, according to air quality monitoring website aqicn.org, or nearly 20 times the World Health Organisation's recommended daily maximum exposure.

The high levels pose a threat to human health, and the city urged children and the elderly to stay indoors.

The storm will cover large portions of the country's northwest through tomorrow, according to state broadcaster CCTV.

Beijing has attempted to combat the phenomenon with greenbelts around the city, but increased desertification in the country's northwest have frustrated the efforts.